Bolt Support Research Articles

Thickness and Strength Analysis of Prestressed Anchor (Cable) Compression Arch Based on Safe Co-Mining of Deep Coal and Gas

The stability of the gas extraction roadway is very important for the safe mining of coal and gas. The compression arch formed by the combined action of the prestressed bolt (cable) support and surrounding rock has been widely used in the engineering practice of the gas extraction roadway. It is of great engineering application value to analyze the influence of prestressed bolt (cable) parameters on the compression arch. In this paper, combined with the engineering practice of the deep roadway in Huainan and Huaibei mining area of Anhui Province, the mechanical parameters of surrounding rock are measured via field coring and the laboratory. The numerical simulation software FLAC3D is used to analyze the typical position of fractured mudstone, mudstone, sandy mudstone and muddy sandstone under the bolt pre-tightening force of F = 50 kN, 70 kN and 100 kN; the bolt spacing of a × b = 400 mm × 400 mm, 500 mm × 500 mm and 600 mm × 600 mm; the bolt length of L = 1500 mm, 2000 mm, 2600 mm and 3000 mm; and the distribution characteristics of additional compressive stress on the surface of the side. The influence of the different lithology and bolt parameters on the thickness and strength of the compression arch was analyzed, and on this basis, prestressed anchor cables with a pre-tightening force of F = 80 kN, 100 kN and 120 kN and length of L = 3000 mm, 4000 mm and 6000 mm were applied, and their influence on the thickness and strength of the compression arch was analyzed. The results show that the bolt pre-tightening force (F) and the bolt length (L) have a significant effect on the thickness of the compression arch, while the surrounding rock lithology, the bolt spacing (a × b), the anchor cable pre-tightening force (F) and the anchor cable length (L) have no obvious effect on the thickness of the compression arch. The surrounding rock lithology, the bolt pre-tightening force (F), the bolt length (L), the bolt spacing (a × b), the anchor cable pre-tightening force (F) and the anchor cable length (L) have a significant effect on the strength of the compression arch.

Study on failure behaviors and control technology of surrounding rock in a weakly cemented soft rock roadway: A case study

During coal mining, the deformation and failure of a weakly cemented soft rock roadway roof could cause difficulties for roadway support. In this paper, a combination of on-site measurement and theoretical analysis is used to solve this issue. Firstly this paper investigates the in situ deformation and failure behaviors of a soft rock roadway in a mine in Western China. Then, the failure mechanism and corresponding support principles are discussed and given. Third, various support schemes (bolt and cable reinforcement optimization, grouting, and single prop + top beam combined reinforcement) are proposed and tested. Results show the support capacity can meet the requirements after optimizing the bolt and cable reinforcement support. Due to the development of roof cracks and low grouting pressure, the grouting slurry did not completely fill the roof cracks, resulting in a poor roof control effect. The passive support of a “single prop + top beam” can effectively control the roof subsidence and achieve good application results.

Experiment and Numerical Simulation of Strength and Stress Distribution Behaviors of Anchored Rock Mass in a Roadway

Due to the influence of the ground stress, mining disturbance, and other factors, the roadway surrounding rock in deep underground engineering such as mines, tunnels, and underground caverns is prone to looseness and deformation with the excavation of roadways. In such engineering, the bolt support is frequently employed to stabilize the surrounding rock. In this work, a part of the anchor and the surrounding rock were taken as a simplified model of the anchorage rock mass, and the laboratory compression test was performed on the similitude model. Then, the FLAC3D software was used to simulate varying numbers of bolts and different lateral pressure conditions, and the peak stress, the maximum principal stress field, and the anchor stress field distribution of the anchorage rock mass were obtained. The influence of bolt pretightening force and row spacing on the stability of surrounding rock was discussed using the combined arch theory. The results show that increasing the number of bolts and lateral pressure in the anchorage rock mass can significantly improve the stress value and distribution range of the maximum principal stress field and the anchorage stress field. The fluctuation of the anchorage stress field at different anchorage distances can be lessened by increasing the number of bolts (bolt density). When the lateral pressure exceeds 3 MPa, the anchorage mechanical characteristics of the anchorage rock mass tend to remain stable. The coverage of the effective anchorage stress field and the thickness of the surrounding rock anchorage composite arch can be increased by increasing the bolt pretightening force and decreasing row spacing, consequently improving the anchorage mechanical characteristics of the anchorage rock mass. The research results can be used as a theoretical reference for choosing appropriate bolt support parameters for the roadway surrounding rock.

Stability analysis of rock slope under Sujiaba overpass in Chongqing City based on kinematic and numeric methods

Rock slopes have the characteristics of complex geological conditions, weak structural surface development, steep slope, and great damage. In this study, the Sujiaba overpass slope in Chongqing was selected as the evaluation object, and the main stability evaluation methods of rock slope were analyzed. Combined with the special geological conditions and geographical location of the rock slope, through a geological survey, the slope was qualitatively analyzed based on the stereographic projection method, and the slope stability safety factor was calculated by using the finite element strength reduction method. FLAC3D was used to simulate the initial stress state of the unstable rock mass, the limit state stability of the unstable rock mass before bolt support, and the stability after bolt support. The simulation results show that the stability coefficients of selected unstable rock masses W1, W2, W6, and W7 under the limit state before bolt support are, respectively, 1.22, 1.80, 5.90, and 2.10. Unstable rock masses separate from the parent rock, causing a large displacement due to their instability and downward sliding. After bolt support, stability coefficients for those four unstable rock masses are 1.60, 2.40, 8.60, and 3.20, respectively. Under the same reduction coefficient, rock masses are stable and the displacement is small. The results show that the calculation results of the initial stress state of the rock slope are consistent with the theoretical understanding and field investigation. After the implementation of bolt support, the anti-sliding stability of unstable rock is obviously improved. The research results have important scientific guiding significance and practical value for revealing the failure mechanism of rock slope and analyzing the stability of unstable rock mass.

Characterization of Deformation of Bolts and Induced Stress Wave Propagation under Axial Tensile Stress

The nondestructive testing technique used to evaluate the quality of bolt support by detecting the axial force is suitable for the bolt with a short construction time. For the bolt in the support state for a long time period, it may lead to the detection of small axial force only and ignore the fact that the bolt has entered the necking fracture stage, and thus fail to detect safety hazards in time. Three sets of parallel tests were conducted to solve the misjudgment of detection results due to the reduction of axial force when the bolt was in the necking fracture stage. Bolt deformation characteristics and stress wave propagation characteristics in bolts under axial tensile stress were studied by using the bolt tensile and stress wave detection test system which was modified and built independently. The results showed that (1) The diameter of the necking position decreases continuously during the tensioning process of the bolt and the rate of decrease increases abruptly during the necking fracture stage. (2) Due to the bolt stretching, the stress wave propagates in the bolt with different degrees of reflection and transmission, resulting in the attenuation of the stress wave energy; the energy attenuation ratio of the stress wave signal in the necking fracture stage reaches 35%, and the energy attenuation ratio increases exponentially as the necking continues to occur. (3) The frequency distribution of the stress wave signal during the bolt stretching process is from scattered to concentrated, the dominant frequency is gradually prominent and changes from low frequency to high frequency, the high-frequency signal is more sensitive to the cracks and necking of the bolt, and the dominant frequency is between 9500 and 10,000 Hz. (4) The average error of the stress wave method is 1.945% and the maximum and minimum values are 4.12% and 0.51%, respectively. The method is promising and provides a reference for the study of nondestructive testing of bolt stress waves in field support.

Study on Bursting Liability of Coal-like Material with Pores and Anchors Based on Impact Kinetic Energy Characteristics

Drilling unloading, and bolt support are widely used in the practice of coal mine roadway engineering as the means of impact prevention and support. However, the evaluation index of intact coal body is still used in bursting liability evaluation, and the evaluation results obtained do not match with the actual dynamic phenomena in the field, resulting in inaccurate evaluation results and even bringing serious impact accidents. In this paper, uniaxial compression and uniaxial loading/unloading tests are conducted on specimens in different states, and common evaluation indexes are used to evaluate the bursting liability of specimens in different states, and the impact kinetic energy of crushed blocks during uniaxial compression is calculated. Based on this, the bursting liability criterion based on the impact kinetic energy of the crushed block is established and the common bursting liability evaluation index is modified. The bursting liability obtained by the bursting liability discrimination criterion based on the impact kinetic energy of the crushed block is more consistent with the laboratory dynamic phenomena. Therefore, the bursting liability evaluation results based on the impact kinetic energy of the crushed block are more consistent with the actual engineering. And the numerical simulation results verify the correctness of the bursting liability criterion based on the impact kinetic energy of the crushed block.

Dynamic characteristics and safety control of mortar bolts under tunnel blasting vibration loads

Mortar bolts are an important part of the tunnel support structure, and tunnel blasting can cause vibration hazards to the existing bolt support structure. According to the theory of blasting elastic wave theory, a dynamic mathematical model of bolts mortar bolts considering initial surrounding rock stress was established. Based on the blasting excavation example of the Longnan tunnel of a high-speed railway from Ganzhou to Shenzhen in China, the blasting dynamic response characteristics of mortar bolts in 0 ∼ 3 days, 3 ∼ 7 days, and 7 ∼ 28 days curing time under the blasting excavation of Classification-II, Classification-III, Classification-IV, and Classification-V surrounding rock were calculated and studied. The dynamic failure mechanism of mortar bolts with different curing time under blasting vibration was clarified. According to the limit axial force of the mortar bolts, the blasting safety distance and vibration velocity of the tunnel mortar bolts support structure was proposed.

Technical problems and non destructive testing of rock bolt support systems in mines

The problem of proper assessment of the technical functionality of rock bolt support systems is still valid. Many research centers have undertaken efforts to diagnose and monitor the technical state of such a support system used in mines and tunneling. With that aim the method of quality assessment of grouted rock bolts was invented and a relevant apparatus was constructed. The method concerns non-destructive identification of discontinuity of a resin layer (grout) surrounding rock bolts. The method is based on an impact excitation of a rock bolt and uses modal analysis procedures. Assuming that the installed rock bolt acts as an oscillator, different lengths and positions of grouting discontinuity alter its modal parameters. The extraction of these modal parameters, of which a resonant frequency is seen as the most valued, enable the relevant identification of grout discontinuity. After constructing a prototype version and validating the results for known cases of resin discontinuity in an experimental coal mine, the apparatus fulfilling ATEX requirements was developed. Subsequently that version was also verified both in laboratory conditions and in an experimental coal mine. As necessary for proper identification of discontinuity length, the reference data base was developed and elaborated consisting of a very large number of finite element models (FE models), namely discontinuity cases. The models encountered different rock bolt lengths and diameters, different rock strata parameters and different positions and lengths of resin layers. Then the method was used in a working coal mine to monitor a technical state of rock bolt support system mounted to reinforce long underground openings. The data base was utilized as reference for investigated rock bolts.

Numerical simulation research on bolt supports’ mechanical properties deformation in high-stress roadway

With the rapid development of domestic mining industry, it is necessary to consider the safety of the mine when mining. In order to improve the high stress environment and the frequent failure of bolts caused by the increase of excavation depth, in this experiment, FLAC3D is creatively proposed to establish the calculation model of bolt support roadway, analyze the basic geological environment and surrounding rock structure of the research area, and conduct the numerical simulation of the mechanical characteristics of bolt support deformation (BSD) in the high stress roadway (HSR). The basic geological environment and surrounding rock structure of the study area are analyzed, and FLAC3D is adopted for establishing a calculation model of the bolt-supported roadway, which can be used to simulate the axial and lateral forces of the bolt, and then determine the boundary conditions. It is found that the supporting bolt in the roadway needs to bear not only axial tension, but also transverse shear and bending. Based on the Winkler foundation beam principle, a calculation model of the bolt’s lateral bending force in the soft rock roadway is established, the lateral force characteristics of the bolt support are analyzed, the concept of “anchoring composite bearing body” is proposed, and the force characteristics of the bearing body are calculated. The research results show that in the HSR, the bolt mainly bears the combined forces of tensile and lateral bending; among them, the bolt’s axial force remains basically unchanged at the tail part near the pallet, and the bolt’s axial force at the end part deep into the rock mass decreases rapidly. The bending moment of the bolt is “wave-shaped” distributed along the length of the rod body in the positive direction and negative direction of the axis, and the comprehensive action of the axial tension and transverse bending of the bolt increases when the stress concentration increases. A smaller roadway radius will lead to longer bolts, denser arrangement and higher support strength.

Research on Deformation and Failure Law of the Gob-Side Roadway in Close Extra-Thick Coal Seams

To reveal the deformation and failure law of the gob-side roadway (GSR) and the main influencing factors in close extra-thick coal seams, the research methods of field monitoring, theoretical analysis, and numerical simulation are adopted in this paper. Field monitoring data shows that microseismic events occur and accumulate frequently in the surrounding rock and some overlying key layers of the GSR. Large deformation is experienced in the middle part of roadway near the solid coal side, the middle and upper parts of the roadway near the coal pillar side, and the roadway floor. The overlying strata of the GSR are fractured to form a composite structure as “low-level cantilever beam and high-level masonry beam”. The coal pillar is squeezed and effected by the composite beam structure and the rotation moment M, causing serious bulge in middle and upper part of the coal pillar side. The stability of the solid coal side of the roadway is affected by the stress transferred from gangue contact point. Numerical simulation shows that the immediate roof and key layer breakage are induced by the mining of the 30,501 working face. Shear and tension failures happen in the GSR due to overburden subsidence and rotary extrusion. The stress and displacement at the middle and upper of the roadway on the coal pillar side are larger than the other area. Compared with the solid coal side, the coal on the coal pillar side is obviously more fractured, with a lower bearing capacity. The peak stress in the coal pillar shows up 2 m away from the roadway, which is close to the length of bolt support. The mining-induced stress and the stress transferred from gangue contact point are the direct reasons for solid coal bulge beside the roadway. The peak stress on the solid coal side is located 7 m away from the roadway, at the gangue contact point where overburden fractures. The overburden strata loads and the transferred stress near the gangue contact point are transferred from the sides to the roadway floor. Their coupling effect with the in situ horizontal stress acts as the force source for the plastic floor heave.

Mechanical Analysis of Point Anchored Rock Bolt and Double Linings Support in Circular Hydraulic Tunnel

Mechanical Analysis of Point Anchored Rock Bolt and Double Linings Support in Circular Hydraulic Tunnel

Stability estimation in underground opening with support system using finite–discrete element method-based modeling

The article substantiates the relevance of modeling rock bolt support by the finite–discrete element method for calculating stability of underground mine workings. The mechanics of 1D elements implemented in Prorock program is described. For the real conditions of an underground mine, the method for determining the permissible parameters of support is shown, taking into account the influence of the mining area. The parameters of the artificial stress field were found from the numerical simulation of mining using three different schemes. Schemes 2 and 3 showed more realistic and closer to each other results. Scheme 2 is a finite element simulation with an explicit specification in the caving arch model based on empirical calculations. Scheme 3 assumes modeling by the finite–discrete element method. Scheme 1 shows how the use of FEM can lead to an underestimation of the predicted induced stresses when simulating mining with caving. FDEM modeling of mine workings in various conditions made it possible to determine permissive provisions for the use of compound support systems based on self-attaching frictional rock bolts (manufactured by Ural EnergoResource, Magnitogorsk). The conditions for ensuring stability during construction of mine workings in heavily disturbed and fractured rock masses are demonstrated taking into account the influence of the stoping area. The examples show that, in contrast to FEM, the FDEM models can distinguish between the conditions under which a mine working is in the limiting state and under which it fails. Due to this, the stability reserve as a result of the simulation is determined more accurately, which makes it possible to optimize the parameters of mine support systems based on the FDEM simulation. A case-study describes how FDEM-based modeling allows finding conditions for using a more economical method of supporting underground excavations in comparison with the techniques adopted in the mine.The study was carried out in cooperation with M. V. Kotik, Project Group Manager at Ural EnergoResource, Magnitogorsk, Russia.

Influence of Base-Angle Bolt Support Parameters and Different Sections on Overall Stability of a Roadway under a Deeply Buried High Stress Environment Based on Numerical Simulation

Strengthening the base-angle of a roadway can have a beneficial impact on its overall stability, but the specific optimal parameter selection range is still unclear. Fast Lagrangian Analysis of Continua 3D (FLAC3D) software is used to carry out the stability analysis of 5 kinds of roadway models with different section shapes under the conditions of no support and different base-angle bolt support angles, and the simulation verification is carried out under the actual working conditions of the Sanshandao Gold Mine. The conclusion is as follows: without support, the self-stability of a tri-centric arch roadway is the best, and that of a rectangular roadway is the worst. When the base-angle bolt dip angle is between 15° and 45°, a better supporting effect can be obtained under the established 5 kinds of roadway sections. In the straight wall circular arch roadway of the Sanshandao Gold Mine, the roadway stability is the best when the angle of the base-angle bolt is 15°. However, changing the length of the base-angle bolt, even if the length of the base-angle bolt is increased to a certain extent, will decrease the overall supporting effect of the supporting structure. This paper can provide a reference for the selection of tunnel bottom corner bolt support parameters.

Research on Bolt Support Technology in Soft Coal Seam Roadway

Research on Bolt Support Technology in Soft Coal Seam Roadway

Asymmetric Damage Mechanisms and Prevention Technology in Large-Section Gob-Side Entry Retaining

Based on the deformation and damage characteristics of the surrounding rock in a large-section gob-side entry retaining and combined with field observations and an analysis of the dominant factors, an overall deformation control plan is formulated. The plan mainly includes a structure of high strength, high stiffness and high ductility for roadside support; the reinforcement of the roadway-in support; and the setup entry hydraulic fracturing pressure release mechanism and advanced long, horizontal borehole “fracturing-jet” pressure relief technology. Industrial field tests were completed taking Tangan coal mine as the engineering background. The research shows that the large-section gob-side entry retaining has the typical “asymmetric” overall deformation and damage characteristics, including top coal sinking along the inner side of the roadside support, the whole roadside support structure skewing, and even splitting damage; floor heaving; and the coal-side bolt support structure basically losing support ability and bulging out from the coal side. The dominant factors of deformation damage are disintegration of the floor mudstone by water and deflection deformation under horizontal stress, splitting damage in the concrete roadside support under asymmetric load, damage and expansion due to the insufficient strength of the coal side support, strong dynamic pressure on the roof, and the mutual influence of support and pressure relief. The industrial test shows that the deformation control scheme optimizes the stress environment of the gob-side entry retaining space, the deformation control effect is remarkable, and the roadside fully meets the reuse requirements.

Field test and numerical simulation of initial support effect of negative Poisson's ratio anchor cable under strong impact and vibration

Bolt/cable support technology is widely used in the rock engineering protection field to limit large deformations of surrounding rocks, improve the anti-explosion and anti-impact mechanical properties of engineering rock mass, and increase stability and safety. The underground protective cavern suffers significant damage due to the powerful impact produced by the explosion. This paper studies the macro static and dynamic mechanical properties of the negative Poisson's ratio (NPR) constant resistance and large deformation anchor cable. In addition, an in-situ blasting test scheme is proposed to simulate the approximate plane wave generated by a nuclear explosion in the field. Hence, the anti-explosion and anti-impact properties of the NPR anchor cable support system and failure mode of ternary structure (rod body, anchor body, and rock mass) under explosion influence can be obtained. Finally, numerical modeling is utilized to validate the NPR anchor cable support and PR anchor bolt support under the high vibration condition with the same blasting equivalent. The findings showed that the cavern supported by the NPR anchor cable revealed better overall stability under strong impact and vibration than the PR anchor bolt.

Energy Action Mechanism of Reinforced Sandstone under Triaxial Cyclic Loading and Unloading

In underground engineering, reinforcement is a necessary means to ensure the stability of surrounding rock. Due to the stress redistribution caused by excavation disturbances, the reinforced rock mass is frequently subjected to loading and unloading, and its mechanical properties change accordingly. Based on the above engineering practice, using pasted circular CFRP, an approximate simulation of the rock reinforcement effect of bolt and shotcrete support was performed. Triaxial cyclic loading and unloading tests of reinforced sandstone were carried out, and the influence of different reinforcement schemes on the mechanical properties was compared and analyzed. Furthermore, the strengthening mechanism, damage evolution, and energy transformation mechanism of CFRP are discussed. The results showed that the peak strength increased about 14.2% and 23.8% with the two reinforced schemes, and the residual strength increased about 27.3% and 52.8% with the increase in the area reinforced by CFRP. Under the same confining pressure and strain conditions, the characteristic energy density and elastic energy ratio increased with an increase in the reinforcement area, but the damage variable decreased. It is proved that CFRP can improve energy absorption efficiency, enhance the energy storage limit, and reduce dissipation efficiency. By inhibiting the propagation of internal fissures and limiting the energy dissipation during fractures, the rock mass can be restrained and strengthened.

Mechanical characteristics and stability analysis of surrounding rock reinforcement in rectangular roadway

The stability of surrounding rock with bolt support depends on the stability within the reinforcement range. To understand the reinforcing mechanism of a rectangular roadway bolt fully and accurately, a quantitative method for evaluating the stability of the surrounding rock of a rectangular roadway must be developed. First, a roof beam model of a rectangular tunnel is established according to the deformation law of surrounding rock. Based on the elastic–plastic theory, the deflection calculation formula can be derived, and the ultimate load of the roof beam can be obtained under the plastic state without support. Second, based on the reinforcement effect of bolts, a model of a surrounding rock reinforcement body is established, the physical and mechanical properties of this body are deduced, and a method for evaluating the stability of surrounding rock is derived. Finally, by considering actual engineering cases, the theoretical calculation results of surrounding rock deformation are compared with the numerical simulation and field monitoring results. Moreover, the influence of different parameters of the bolt support on the mechanical characteristics and stability of reinforcement is investigated. The results show that the theoretical calculations approximate the numerical simulation and field monitoring values, thus verifying the rationality of the theory. The physical and mechanical properties and stability of the surrounding rock reinforcement body are considerably affected by changes in bolt length and spacing. The anchor design must apply the following principle: the bolt must either be long and sparsely spaced or short and densely spaced. The theory presented in this paper provides a relatively simple and fast quantitative calculation method for the study of the surrounding rock stability of bolt-supported rectangular roadways.

Spallation damage of underground openings caused by excavation disturbance of adjacent tunnels

Spallation damage in underground mines and tunnels is a common phenomenon, especially during blasting excavations, and revealing the mechanism of spallation damage is an urgent issue for the stability of underground tunnel. In this study, the circumferential and radial stress distributions around the circular tunnel under a transient cylindrical P-wave were examined by combining wave function expansion method and Duhamel’s integral technique. Theoretical results revealed that the spallation damage around the tunnel was mainly caused by high radial dynamic stress concentrations face to a short-wavelength incident waves, and the circumferential and radial stresses around the tunnel decrease as the clearance increases. Furthermore, in order to reappear the spallation damage around the tunnel under blast load and obtain the effect of initial stress and bolt support, the CSCM material model was used to simulate the damage of surrounding rock by LS-DYNA. The numerical simulation results indicated that the initial stress reduced the radial cracks, while the presence of the initial stress exacerbated the spallation damage on the incident side. Finally, the stresses in each time stage of the circular tunnel surrounding rock under the action of transient cylindrical P-waves were analysed.

Analysis of Surrounding Rock Control Technology and Its Application on a Dynamic Pressure Roadway in a Thick Coal Seam

The deformation control of roadways surrounded by rock in the fully mechanized amplification sections of extra-thick coal seams is problematic. To analyze the failure and failure characteristics of a support frame, as well as the deformation and failure processes of the surrounding rock, through theoretical analysis and industrial tests, the deformation and support conditions of a return airway of a fully mechanized caving face in an extra-thick coal seam in the Yangchangwan Coal Mine, in the Ningdong mining, area were examined. Combined with limit equilibrium theory and roadway section size, the width of the coal pillar of the return air roadway at the 130,205 working face was calculated to be 6 m. The layout scheme and implementation parameters of roof blasting pressure relief, coal pillar grouting modification, and bolt (cable) support were designed. Based on the analysis, a “Coal pillar optimization–roof cutting destressing–routing modification–rock bolting” system for surrounding rock control in synergy with the fully enlarged section mining roadway in the extra-thick coal seam was proposed, and the deformation of the surrounding rock was monitored, along with the stress of the support body and the grouting effect on the site. Field experiments show that after the implementation of the surrounding rock control in synergy with the roadway, the maximum subsidence of the top plate was 55 mm, the maximum bottom heave of the bottom plate was 55 mm, the maximum values of the upper and lower side drums were 30 mm and 70 mm, respectively, and the breaking rate of the bolt (cable) and the deformation of the surrounding rock of the roadway was reduced by more than 90% and 70%, respectively. The effective performance of the coal pillar grouting was observed as well. Field practice of the roadway surrounding rock control in the synergy method indicated that rock deformation was effectively controlled, and the successful application of this technology was able to provide reliable technical and theoretical support for the Ningdong mining area and mines with similar conditions.